OS X says I don't have enough hard drive space to put trashed files back?

I dragged my son's profile folder into the trash but want to put it back. The folder is about 120gb. When I try to drag it back to its original location, it says I don't have enough hard drive space (which would be true if I was trying to copy it - I only have about 5gb free). I figured since it's not totally deleted from my drive, the amount of free space would be irrelevant.

What's the deal?

Thanks!